Dehydrations of cis- and trans-2-methylcyclohexanol mixtures were carried out with 60% sulfuric acid at 78−80 °C as a function of time and the products were identified by gas chromatography−mass spectroscopy (GC−MS) analysis. The compounds identified in the reaction mixtures include alkenes, 1-, 3-, and 4-methylcyclohexenes and 1-ethylcyclopentene, as well as the alcohols, 1-, 3-, and 4-methylcyclohexanols, and residual starting material. Independent reactions under identical conditions of the pure cis- and trans-2-methylcyclohexanol isomers, 1-, 3- and 4-methylcyclohexanol were also carried out. These reactions reveal that the cis-isomer reacts predominately to form 1-methylcyclohexene whereas the trans-isomer reacts to give a complicated mixture consisting of the isomeric 1-, 3-, and 4-methylcyclohexanols, 1-, 3-, and 4-methylcyclohexenes, and the ring contraction product, 1-ethylcyclopentene. In the experiment, each student carries out a dehydration of the cis- and trans-2-methylcyclohexanol mixture or of one of the pure isomers and the results from the GC−MS analyses of the whole class are pooled. The analysis reinforces lecture material and provides an appreciation of the complexity of elimination−dehydration reactions that proceed via carbocation intermediates and can undergo intricate rearrangements such as hydride and alkyl shifts. The reaction procedure is straightforward and the GC−MS analysis simple enough so it can easily be used in the first semester of undergraduate organic chemistry laboratory.

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The nitration of six benzene derivatives having a range of substituents that differ in electronic effects were followed by GC–MS analyses of the crude reaction mixtures and adapted for the second-year organic laboratory. Students pool their results and identify the products by analyzing the mass spectral data of the isomers and by comparing them to the GC–MS analysis of authentic samples. Students determine which substituents predominantly direct nitration to the ortho- or para- and to the meta positions. This simple discovery-oriented experiment illustrates and reinforces the lecture material and provides students with first-hand knowledge of how textbook conclusions are determined in a laboratory situation.